These will be operated by regional carriers. It's a common practice for DL to own regional aircraft and then contract regionals to fly them. It's good negotiating leverage because if the regional doesnt offer a good rate DL can take the planes away and give them to someone else.

Not ALL, there's a lot of markets that don't need the seats of the bigger RJ's. But they want to get down to around 100 50 seaters, most of which will probably be operated by Pinnacle (since the 9E CRJ's are owned by DL and were mostly delivered in the 2000's to NW).

Will be interesting to see if they eventually replace more CRJ200s with Q400s or something similar. From what I recall I remember hearing that RJs were great when they first came out but then fuel went up. Hopefully more airlines start following in Delta's footsteps and replace higher capicity routes with the CRJ900s. I was on a flight back in April I think from PHX to OAK on US Airways operated by SkyWest on a 200. I think a few months later SkyWest stopped operating the route between PHX and OAK. I see why. Haha. Made no sense to fly a 200 between two largish cities and I think the flight was overbooked. Mesa flies the 900 to OAK now from PHX. Makes more sense.

Does this mean Delta is planning to operate these CR9s as part of their mainline fleet? (Since Delta is the one doing the ordering, and they no longer have a wholly owned regional airline to give them to.)

DL is still a possibility to order the MAX, but they rarely order an aircraft before its first flight (it's risky to plan your future on an aircraft that doesn't yet exist). The MAX is still years away.

This order was also necessary in order for Bombardier to take back CRJ-200's that DL is looking to rid itself of based on its future fleet plans. They were also likely obtained at a very low price since Bombardier only had ~50-60 frames on the CRJ line backlog and the line faced closure within the next year or 2 without any new orders.